For complex data processing systems which are coupled together, the operating speeds of the individual data processing systems may vary. Therefore to synchronize the systems, it is not sufficient enough to merely start the program runs simultaneously. Rather, steps must be taken to ensure synchronization throughout the duration of time in which the program is running.
German Published Patent Application 36 33 953 discloses the use of two identical program runs in a program-controlled automating device having a redundant set up using two subsystems. The device implements a reciprocal synchronization of the program runs from the operating system at the beginning of certain program sections.
When the identical programs are subdivided into program sections, it sometimes becomes necessary to only synchronize the data processing systems at later points in time rather than at the beginning of a new program section, or to synchronize even before the beginning of the next new program section.
There is therefore needed a method for synchronizing data processing systems, whereby a synchronization operation is only undertaken when necessary to provide program synchronism for the data processing systems.